CentOS - Nov 2020 - Error from unix_chkpwd

Hi,
On CentOS 7.7.1908 I've got the following error message:
unix_chkpwd[1026]: could not obtain user info (root)

I dont' know why...

There are no SELinux errors, and the permissions of relevant files are:
ls -Z /etc/shadow /etc/passwd /usr/sbin/unix_chkpwd
-rw-r--r--. root root system_u:object_r:passwd_file_t:s0 /etc/passwd
----------. root root system_u:object_r:shadow_t:s0    /etc/shadow
-rwsr-xr-x. root root system_u:object_r:chkpwd_exec_t:s0
/usr/sbin/unix_chkpwd


Any idea?

Thanks in advance!
-- 
--
Sergio Belkin
LPIC-2 Certified - http://www.lpi.org